The present invention relates to improvements of wind energy turbines and, in particular, to a device for driving a first part of a wind energy turbine with respect to a second part of the wind energy turbine or vice versa.
Modern wind energy turbines are provided with pitch and yaw drives. By means of the yaw drive it is possible to azimuthally drive the nacelle of a wind energy turbine with respect to its tower rotatably supporting the nacelle. A pitch drive is used to adjust the rotor blade of a wind energy turbine rotor. For each rotor blade usually one separate pitch drive is provided.
Both pitch and yaw drives of wind energy turbines have brakes on the motion generating means which normally includes an electrical motor. Moreover, the electrical motor often includes the brake system. Additionally or alternatively brakes may be built on the bearing structure between the first and second part. The brakes of the pitch and yaw drives of a wind energy turbine are operable to prevent unallowed relative rotation of the one part (rotor blade or nacelle) with respect to the other part (hub or tower, respectively). However, it may happen that wind forces act on the rotor blade and nacelle which wind forces result in torques acting on the blade or on the nacelle which are higher than the break-loose torques. Since the inertia of the elements of the pitch and yaw drives are significant, the torques on the elements of the drives can rise to levels higher than the break-loose torque which may damage the drives.
It is known to provide the connection of the housing of a yaw drive to the nacelle with a slip coupling. If this coupling slips due to high wind forces acting on the nacelle, the complete housing of the yaw drive rotates with respect to the nacelle so that the electrical cables and, if provided, hydraulic conduits have to be designed accordingly to compensate for the rotation. This complicates the construction of the yaw drive.